In the coverage of a traditional Multiple Frequency Network, a signal is transmitted by a transmitter in a service area at different frequencies to avoid interference between neighboring transmitters. A broadcast service such as a Multimedia Broadcast Multicast Service (MBMS) typically occupies a relatively broad frequency band due to the large amount of transmitted data. Therefore, the broadcast service is implemented usually using a scheme of single frequency coverage, i.e. a Single Frequency Network (SFN), in the prior art.
In the Single Frequency Network, multiple synchronous radio transmitters at different sites transmit the same signal at the same frequency concurrently, to implement reliable coverage of a certain service area.
First, the Single Frequency Network is advantageous in frequency planning, so that the precious frequency resources can be saved significantly and the utilization of the frequency spectrum can be improved. Secondly, in a city with lots of high buildings, there exist numerous areas without the coverage of a radio signal due to the property of the radio signal per se regardless of the large transmission power of the single transmitter station, such an area without the coverage of the radio signal may be referred to as a blind coverage area or blink area, and can be eliminated in such a manner that the signal is transmitted over the same frequency at multiple stations in the Single Frequency Network, to obtain improved coverage. Thirdly, the Single Frequency Network technologies enable the reduction of costs of the transmitter device in that multiple transmitters with small power instead of one transmitter with large power can be adopted by optimizing and adjusting the transmission network (such as the number and distribution of base stations, the height of transmission antennae, and transmission power) in the Single Frequency Network, thereby reducing signal radiation and electromagnetic wave pollution, and improving coverage uniformity; in addition, the intended coverage can be modified as desired at any time.
In the Single Frequency Network, merely one frequency band is required for the multiple transmitters to transmit one signal, so that the frequency resources can be saved greatly. A User Equipment (UE) can process signals from the multiple base stations as multi-path signals. It is possible that particular time slots are designated for the MBMS service. Further, diversity is achieved by the simultaneous transmission of the multiple transmitters, so that the reliability of the receiver can be enhanced effectively to obtain the coverage required for reliable service. Additionally, the transmission network can be adjusted and optimized as desired, so that the total power consumption can be lowered, and the interference with any other network in the environment can be reduced.
At present, the Single Frequency Network is controlled in a static manner in the prior art, that is, base stations and the number thereof within a given Single Frequency Network are consistent. Or, the Single Frequency Network can be controlled in such a dynamic manner that a simple “switch on/off” mode is available, that is, the base stations within the Single Frequency Network can be managed in the “switch on/off” mode, and a certain base station is either switched on to implement various services configured at the Single Frequency Network or switched off to no longer implement the services configured at the Single Frequency Network. Therefore, it is very difficult for an operator to effectively optimize wireless network resources in the prior art, and it is impossible to allocate resources based on service requirements of users.